The present invention relates to a stabilization device for the dynamic stabilization of vertebrae or bones, and a rod-like element used in this stabilization device.
European Patent Application, EP 1 188 416 A1, discloses a dynamic stabilization device for stabilizing neighboring thoracic vertebra. The device comprises two pedicle screws and a cable-like strap (31), which is attached to the receiving part of the pedicle screw by a clamping screw. The device also contains a support element (3) in the form of a pressure-resistant body that is mounted on the strap.
U.S. Patent Publication 2003/0109880 A1 describes a dynamic stabilization device for vertebrae which comprises a first and a second screw to be anchored in a vertebra. A coil spring (11) connects an upper portion of the first screw and the upper portion of the second screw.
U.S. Pat. No. 5,415,661 describes an implantable spinal assist device which includes a body composed of a composite material made up of a fiber material interspersed in a matrix material. The body is curved along its longitudinal axis and comprises a curved center section unattached to a motion segment unit and a pair of opposed terminal sections. Similarly, U.S. Patent Publication 2003/0191470 A1 discloses a dynamic fixation device. The device includes a flexible portion and two ends that are adapted for connection to pedicle screws. In both of these references, the curved elastic rod, which is anchored at its ends on neighboring vertebrae on the same side of the spinal column by means of anchoring elements with a shaft of the pedicle screws. Therefore, the curved elastic rods face in the anterior/posterior direction. The curvature fulfils the function of a spring rod.
The known stabilization devices each use two of these stabilization devices for stabilizing two neighboring vertebrae with the stabilization devices being anchored to the right and to the left of the middle longitudinal axis of the spinal column.
U.S. Pat. No. 6,440,169 B1, describes a stabilization device for the spinal column, which comprises an elastic body in the form of a leaf spring which extends between anchoring points in neighboring vertebrae and is shaped such that it forms the wall of an orifice, whereby the orifice faces in the anterior/posterior direction with respect to the body of the patient and is closed in the medial/lateral direction.
It is it is desirable to support the disk in a defined fashion with respect to the transmitted forces and to control the motion by means of a posterior dynamic stabilization device, especially in the presence of a damaged or an artificial intervertebral disk. In this regard, a flexion and an extension of the spinal column or of the element containing the respective intervertebral disk, as shown in FIG. 8a, is desired, whereas lateral translational motion as well as a torsional motion around the middle longitudinal axis of the spinal column, as shown in FIG. 8b, is undesired.